NDARC Technical Report No. 69 (1998)
This report analyses data on trends in opioid overdose deaths in general, and methadone deaths in particular, in the United Kingdom (UK) between 1985 and 1995. It places these trends in the context of the epidemiology of opioid dependence in the UK, the risks and benefits of methadone maintenance treatment for opioid dependence, and the risk factors for opioid overdose death.
The report begins with a description of the pharmacology and toxicology of the opioid agonist methadone. It describes its therapeutic uses in assisting opioid dependent persons to withdraw from heroin and its use as a maintenance treatment for opioid dependence. The benefits of methadone maintenance treatment for opioid dependent persons and the community are briefly summarised. The epidemiology of opioid and methadone overdose deaths is briefly reviewed. A distinction is made between methadone-related deaths that occur among persons who are enrolled in methadone maintenance treatment and deaths that occur among opiate users who have used diverted methadone.
The core of the report is an analysis of trends in heroin and methadone-related deaths in the UK between 1985 and 1995. Analyses are reported on trends in population mortality rates and the proportion of all deaths attributable to opioid overdose in the UK between 1985-1995. A comparison is also made of trends in opioid overdose and methadone overdose deaths in the UK and Australia. The comparison indicated that the two countries showed an overall increase in opioid overdose deaths between 1985 and 1995 with two important differences in pattern: (1) the UK had lower rate of opioid overdose deaths than Australia but (2) methadone played a contributory role in a larger proportion of opioid overdose deaths in the UK than Australia.
In the final section of the report some provisional conclusions are drawn about trends in the overall rate of methadone-related deaths in the United Kingdom over the period 1985-1995. The most plausible explanation of these trends is that the number of opioid dependent persons in the UK has increased over the period. The high rate of methadone involvement in these deaths probably reflects the greater availability of methadone and lower rate of supervised methadone dosing in the UK than Australia.
There are a number of possible explanations of the higher opioid overdose mortality in Australia, and the apparently lower rate of methadone involvement in these deaths. These possibilities cannot be distinguished on the basis of the available data. These are: that they are an artefact of different methods of classifying causes of death involving opioid drugs in Australia and the UK; that the UK has a much lower rate of opioid dependence, or a different pattern of dependence (e.g. much fewer heroin injectors) than Australia; and that the widespread availability of methadone in the UK has reduced the overall rate of opioid overdose deaths by increasing the number of dependent drug users who are in treatment, at the cost of increasing the proportion of overdose deaths in which methadone plays a role. The report identifies priorities for future research on opioid overdose and methadonerelated overdose deaths in the UK, and makes some suggestions as to how the rate of methadone-related overdose deaths in the UK may be reduced.